Design and Properties of Azaacene-Fused Porphyrins: Extending π-Systems for NIR-II Absorption.

A series of porphyrins featuring various azaacene moieties were designed with the aim to explore the structure-property relationships in extended azaacene systems. The introduction of azaacene groups significantly enhanced the solubility of these chromophores while directly influencing their electronic absorption and emission properties, enabling absorption at longer wavelengths. Protonation of the azaacene-fused porphyrins further extended their absorption into the NIR-II region.

Coupled Polymethine Dyes: Six Decades of Discoveries.

This review provides a comprehensive examination of the applications of the seminal coupling principle introduced by Siegfried Dähne and Dieter Leupold in 1966. Their heuristic and groundbreaking work proposed that combining multiple polymethine subunits within a single chromophore enables orbital coupling, consequently narrowing the HOMO-LUMO gap, and yielding redshifted optical properties. These outcomes are particularly valuable for developing organic dyes tailored for visible-to-near-infrared applications.

Insights into extended coupled polymethines through the investigation of dual UV-to-NIR acidochromic switches based on heptamethine-oxonol dyes.

A series of heptamethine-oxonol dyes featuring different heterocyclic end groups were designed with the aim to explore structure-property relationships in π-extended coupled polymethines. These dyes can be stabilised under three different protonation states, affording dicationic derivatives with an aromatic core, cationic heptamethines, and zwitterionic bis-cyanine forms. The variation of the end groups directly impacts the absorption and emission properties and mostly controls reaching either a colourless neutral dispirocyclic species or near-infrared zwitterions.

Breaking Azacalix[4]arenes into Induline Derivatives.

Tetraamino-tetranitro-azacalixarene is at the crossroad of two different families of compounds depending on the conditions and the agent used to reduce the NO groups: (1) azacalixphyrin in neutral medium, or (2) phenazinium of type in acidic medium. The key role of the N-substituted amino functions at the periphery is highlighted by investigating octaaminoazacalixarene as a model compound, and by using the corresponding tetrahydroxy-tetranitro-azacalixarene as a precursor, which behaves differently.

Tris-benzo[cd]indole Cyanine Enables the NIR-photosensitized Radical and Thiol-ene Polymerizations at 940 nm.

A near-infrared-absorbing heptamethine (HM ) incorporating three bulky benzo[cd]indole heterocycles was designed to efficiently prevent self-aggregation of the dye, which results in a strong enhancement of its photoinitiating reactivity as compared to a parent bis-benzo[cd]indole heptamethine (HMCl ) used as a reference system. In this context, we highlight an efficient free-radical NIR-polymerization up to a 100 % acrylates C=C bonds conversion even under air conditions. Such an important initiating performance was obtained by incorporating our NIR-sensitizer into a three-component system leading to its self-regeneration.